Method and device for compression moulding a closure cap

ABSTRACT

A method and device for the production of a closure cap having a first part ( 16, 17 ) and a second part ( 18 ), joined together by at least one thinner section ( 19 ). The device contains a female mould part ( 11 ) and a male mould part ( 12 ), which are moveable relative to one another, in order to enclose a mould cavity. After the closing of the mould cavity, an additional mould part ( 14 ) is moveable relative to the mould cavity. In order to reduce the volume thereof, until the plastics material fills the mould cavity completely. Consequently the invention ensures that when compression moulding in the mould cavity, the closure cap and in particular also the thinner section ( 19 ) are formed completely in the mould provided.

BACKGROUND OF THE INVENTION

The invention concerns a method and a device for compression moulding acontainer closure cap, which has a first part and a second part, whichare joined together by at least one thinner section. For example, aclosure cap having a body and a tamper evident band joined together bythin frangible bridges or a closure cap having a body and a lidconnected by a thin hinge section.

SUMMARY OF THE INVENTION

The aim of the invention is to design a method and apparatus so as toguarantee that during compression moulding, the closure cap and inparticular the thinner section or sections are formed completely in themould cavity provided, without it being necessary to insert excessplastics material into the mould, which is then pressed out of the mouldupon closing of the mould cavity.

Examples of the invention are explained below with reference to theaccompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of a female mould part and amale mould part of a compression moulding device according to theinvention in a closed position.

FIG. 2 shows the female mould part and the male mould part of FIG. 1 ina final position.

FIG. 3 shows a female mould part and a male mould part of anotherembodiment of the compression moulding device in a closed position.

FIG. 4 shows the female mould part and the male mould part of FIG. 3 ina final position.

FIG. 5 shows the female mould part and the male mould part of a thirdembodiment of the compression moulding machine in a closed position and

FIG. 6 shows the female mould part and the male mould part of FIG. 5 ina final position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show schematically a female mould part 11 and a male mouldpart 12, which are axially moveable relative to one another. In theiropen position (not represented), the female mould part 11 and the malemould part 12 are separated by a distance from one another. A portion ofsoftened plastics material is fed into the female mould part, whilst themould is in this open position.

The female mould part 11 and the male mould part 12 are then movedrelative to one another (by means not represented) into the closedposition shown in FIG. 1, where a circumferential edge of the male mouldpart lies on an upper edge of the female mould part. In this position,the female mould part and male mould part define a mould cavity betweenone another, in the form of a container closure cap. In the positionshown in FIG. 1 the plastics material 13 does not yet fill the mouldcavity completely.

An additional mould part 14 is arranged in the female mould part 11. Themould part 14 is moveable relative to the mould cavity by means of ahydraulic ram 15, in order to reduce the volume of the mould cavity,until the plastics material 13 fills the mould cavity completely, asshown in FIG. 2. The finished container closure cap represented in FIG.2 has a first part in the form of a bottom end 16 and a circumferentialwall 17 extending from the bottom end, a second part in the form of anannular element 18 and at least one thinner section 19 joining the twoparts together. The mould cavity correspondingly has a first cavity partfor forming the first part 16, 17 of the closure cap, a second cavitypart for forming the second part 18 of the closure cap and anintermediate cavity part for forming the thinner section 19.

After closing the mould cavity, the position shown in FIG. 1, theplastics material (from the portion of plastics material fed in to themould cavity when the male and female mould parts were in their openposition) fills the first cavity part, which forms the first part, 16,17 of the closure cap. As a rule, the plastics material fills the firstcavity part virtually completely, but does not fill or at most partlyfills the second cavity part (which forms the second part 18 of theclosure cap) and the intermediate cavity part (which forms the thinnersection 19). Upon movement of the additional mould part 14 to reduce thevolume of the mould cavity, part of the plastics material is thenpressed out of the first cavity part through the intermediate cavitypart and into the second cavity part, until the plastics material fillsthe whole mould cavity completely.

The annular element 18 may be, for example, a tamper evident band, whichis joined to the circumferential wall 17 via a thinner section 19 in theform of a predetermined breaking line or line of weakening, so that uponthe removal of the closure cap from a container the tamper evident band18 is separated from the circumferential wall 17. Such a predeterminedbreaking line 19 is in a narrow area of the mould cavity, in which theplastics material is only thin and if necessary also has openings, sothat the line of weakening 19 is defined by a plurality of thin,frangible bridges.

In the example described above, the additional mould part 14 is arrangedin the female mould part 11. However, the additional mould part (forreducing the volume of the mould cavity after closing of the same) couldalso be arranged, with equal effect in the male mould part 12 instead ofin the female mould part 11.

The embodiment of the compression moulding device according to FIGS. 3and 4 contains the same elements as the device according to FIGS. 1 and2, and these elements are designated with the same reference numbers asin FIGS. 1 and 2.

Unlike the device according to FIGS. 1 and 2, in the device according toFIGS. 3 and 4 a second additional mould part 20 is arranged in the malemould part 12. The second additional mould part 20 is moveable in themale mould part 12 against the action of a force F. In the deviceaccording to FIGS. 3 and 4, after the mould cavity is closed by thehydraulic ram 15, the first additional mould part 14 is moved into apredetermined final position, reducing the volume of the mould cavity,until the plastics material fills the whole mould cavity completely. Thepre-determined final position in the example is defined by a band 21, onthe additional mould part 14, knocking against a counter-face 22 (FIG.3) on the female mould part 11.

The second additional mould part 20, is shifted against the action ofthe force F by the pressure of the plastics material 13, which isproduced by the movement of the first additional mould part 14. Thus,the second additional mould part 20 is used for volume equalisation,which means that the final volume of the mould cavity is adapted exactlyto the size of the portion of plastics material fed into the mouldcavity. The final pressure of the plastics material 13 produced in themould cavity is controlled by the size of the force F.

Through the predetermined final position of the first additional mouldpart 14 moveable in the female mould 11, the external shape of theclosure cap formed, is precisely predetermined, regardless of anydeviations from a nominal size occurring in the size of the portion ofplastics material fed into the mould cavity.

The device according to FIGS. 5 and 6 again contains the secondadditional mould part 20 moveable in the male mould part 12 against theaction of the force F. The male mould part 12 and a female mould part111 are axially movable relative to one another. In the closed positionrepresented, a circumferential part of the male mould part 12 lies on anupper edge of the female mould part 111, the male mould part and thefemale mould part define a mould cavity between one another in the shapeof a container closure cap. The female mould part 111 is held such thatit can move axially in a holder part 110 and is spring-loaded withregard to the holder part 110 in the final position shown in FIG. 5 bymeans of a compression spring 109.

A cylindrical projection 114 of the holder part 110 projects into thefemale mould part 111 and forms a first additional mould part. Thefemale mould part 111 (and the mould cavity formed therein) and theadditional mould part 114 are moveable axially relative to one anotheragainst the action of the spring 109, in order to reduce the volume ofthe mould cavity, until the plastics material 13 fills the whole cavitycompletely as shown in FIG. 6. This movement takes place through thefact that means (not represented) for closing the mould cavity pressesthe circumferential part of the male mould part 12 on to the upper edgeof the female mould part 111, and moves the female and male mould partsand thereby the mould cavity further together into the holder part 110.After this movement, the mould cavity and the first additional mouldpart 114 have a predetermined final position relative to one another(FIG. 6), which is defined in this example through the fact that a loweredge of the female mould part 111 knocks against a counter-face 122 ofthe holder part 110.

The purpose and effect of the second additional mould part 20 in thedevice according to FIGS. 5 and 6 are the same as in the deviceaccording to FIGS. 3 and 4.

Although a preferred embodiment of the invention has been specificallyillustrated and described herein, it is to be understood that minorvariations may be made in the apparatus without departing from thespirit and scope of the invention, as defined by the appended claims.

1. A method for compression moulding a container closure cap, which hasa first part (16, 17) and a second part (18), which are joined togetherby at least one thinner section (19), characterised by the followingsteps: Preparing a mould with a female mould part (11; 111) and a malemould part (12), which are moveable relative to one another, in order toenclose there between a mould cavity, which has a first mould part forforming the first part (16, 17) of the closure cap, a second mould partfor forming the second part (18) of the closure cap and a intermediatecavity part for forming the thinner section (19), Feeding a portion ofplastics material into the female mould part (11; 111), Moving thefemale mould part (11; 111) and the male mould part (12) relative to oneanother to close the mould cavity, Moving an additional mould part (14;114) relative to the mould cavity in such a way that the volume of themould cavity is reduced and a part of the portion of plastics materialis pressed from the first cavity part through the intermediate cavitypart into the second cavity part, in order to form the thinner section(19) and the second part (18) of the closure cap.
 2. A method accordingto claim 1, for compression moulding a container closure cap, in whichthe first part (16, 17) defines a bottom end and a circumferential walland the second part (18) defines an annular element.
 3. A device forcompression moulding of a container closure cap, which has a first part(16, 17) and a second part (18), which are joined together by at leastone thinner section (19), characterised by a female mould part (11; 111)and a male mould part (12), which are moveable relative to one another,in order to enclose a mould cavity, which has a first cavity part forforming the first part (16, 17) of the closure cap, a second cavity partfor forming the second part (18) of the closure cap and an intermediatecavity part for forming the thinner section (19), and an additionalmould part (14; 114), which after the closing of the mould cavity ismoveable relative to the mould cavity, in order to reduce the volume ofthe mould cavity and to press plastics material (13) out of the firstcavity part through the intermediate cavity part into the second cavitypart, until the plastics material fills the mould cavity completely. 4.A device according to claim 3, characterised in that the first cavitypart is formed for moulding a bottom end (16) and a circumferential wall(17) of the closure cap and the second cavity part is formed formoulding an annular element (18) of the closure cap.
 5. A deviceaccording to claim 4, characterised in that the second cavity part isformed for moulding a tamper evident band (18) and the intermediatecavity part is formed for moulding a nominal breaking line (19) betweenthe circumferential wall (17) and the tamper evident band (18).
 6. Adevice according to claim 3, characterised by a second additional mouldpart (20), which after the complete filling of the mould cavity ismoveable in response to the pressure of the plastics material (13) inthe mould cavity.
 7. A device according to claim 6, characterised inthat, after the closing of the mould cavity, the first-mentionedadditional mould part (14; 114) is moveable into a predetermined finalposition.
 8. A device according to claim 6, characterised in that thefirst-mentioned additional mould part (14; 114) is moveable axially inthe female mould part (11; 111) and the second additional mould part(20) is moveable axially in the male mould part (12).
 9. A deviceaccording to claim 4, characterised by a second additional mould part(20), which after the complete filling of the mould cavity is moveablein response to the pressure of the plastics material (13) in the mouldcavity.
 10. A device according to claim 5, characterised by a secondadditional mould part (20), which after the complete filling of themould cavity is moveable in response to the pressure of the plasticsmaterial (13) in the mould cavity.
 11. A device according to claim 7,characterised in that the first-mentioned additional mould part (14;114) is moveable axially in the female mould part (11; 111) and thesecond additional mould part (20) is moveable axially in the male mouldpart (12).